GC: Ptr clean-up and Invalid NextLink logging (#2547)

## Description
- Use of ptr package for next link and delta links. 
- Added logging to verify the presence of receiving invalid next links from M365.


<!-- Insert PR description-->

## Does this PR need a docs update or release note?

- [x] ⛔ No 

- Related to #2520
## Type of change
- [x] 🧹 Tech Debt/Cleanup

## Test Plan

<!-- How will this be tested prior to merging.-->
- [x] ⚡ Unit test

src/internal/connector/exchange/api/shared.go

@@ -3,6 +3,7 @@ package api
 import (
 	"context"
 	"fmt"
+	"os"
 
 	"github.com/alcionai/clues"
 
@@ -104,6 +105,11 @@ func getItemsAddedAndRemovedFromContainer(
 		}
 
 		nextLink, delta := api.NextAndDeltaLink(resp)
+		if len(os.Getenv("CORSO_URL_LOGGING")) > 0 {
+			if !api.IsNextLinkValid(nextLink) || api.IsNextLinkValid(delta) {
+				logger.Ctx(ctx).Infof("Received invalid link from M365:\nNext Link: %s\nDelta Link: %s\n", nextLink, delta)
+			}
+		}
 
 		// the deltaLink is kind of like a cursor for overall data state.
 		// once we run through pages of nextLinks, the last query will

src/internal/connector/graph/api/api.go

@@ -1,6 +1,10 @@
 package api
 
-import "github.com/alcionai/corso/src/internal/common/ptr"
+import (
+	"strings"
+
+	"github.com/alcionai/corso/src/internal/common/ptr"
+)
 
 type PageLinker interface {
 	GetOdataNextLink() *string
@@ -11,6 +15,11 @@ type DeltaPageLinker interface {
 	GetOdataDeltaLink() *string
 }
 
+// IsNextLinkValid separate check to investigate whether error is
+func IsNextLinkValid(next string) bool {
+	return !strings.Contains(next, `users//`)
+}
+
 func NextLink(pl PageLinker) string {
 	return ptr.Val(pl.GetOdataNextLink())
 }

src/internal/connector/graph/api/api_test.go

@@ -8,6 +8,7 @@ import (
 	"github.com/stretchr/testify/suite"
 
 	"github.com/alcionai/corso/src/internal/connector/graph/api"
+	"github.com/alcionai/corso/src/internal/tester"
 )
 
 type mockNextLink struct {
@@ -59,20 +60,14 @@ var (
 )
 
 type APIUnitSuite struct {
-	suite.Suite
+	tester.Suite
 }
 
 func TestAPIUnitSuite(t *testing.T) {
-	suite.Run(t, new(APIUnitSuite))
-}
-
-func (suite *APIUnitSuite) TestNextLink() {
-	for _, test := range nextLinkInputs {
-		suite.T().Run(test.name, func(t *testing.T) {
-			l := mockNextLink{nextLink: test.inputLink}
-			assert.Equal(t, test.expectedLink, api.NextLink(l))
-		})
+	s := &APIUnitSuite{
+		Suite: tester.NewUnitSuite(t),
 	}
+	suite.Run(t, s)
 }
 
 func (suite *APIUnitSuite) TestNextAndDeltaLink() {
@@ -112,3 +107,39 @@ func (suite *APIUnitSuite) TestNextAndDeltaLink() {
 		}
 	}
 }
+
+// TestIsLinkValid check to verify is nextLink guard check for logging
+// Related to: https://github.com/alcionai/corso/issues/2520
+//
+//nolint:lll
+func (suite *APIUnitSuite) TestIsLinkValid() {
+	invalidString := `https://graph.microsoft.com/v1.0/users//mailFolders//messages/microsoft.graph.delta()?$select=id%2CisRead`
+	tests := []struct {
+		name        string
+		inputString string
+		isValid     assert.BoolAssertionFunc
+	}{
+		{
+			name:        "Empty",
+			inputString: emptyLink,
+			isValid:     assert.True,
+		},
+		{
+			name:        "Invalid",
+			inputString: invalidString,
+			isValid:     assert.False,
+		},
+		{
+			name:        "Valid",
+			inputString: `https://graph.microsoft.com/v1.0/users/aPerson/mailFolders/AMessage/messages/microsoft.graph.delta()?$select=id%2CisRead`,
+			isValid:     assert.True,
+		},
+	}
+
+	for _, test := range tests {
+		suite.T().Run(test.name, func(t *testing.T) {
+			got := api.IsNextLinkValid(test.inputString)
+			test.isValid(t, got)
+		})
+	}
+}

src/internal/connector/onedrive/drive.go

@@ -12,6 +12,7 @@ import (
 	"github.com/pkg/errors"
 	"golang.org/x/exp/maps"
 
+	"github.com/alcionai/corso/src/internal/common/ptr"
 	"github.com/alcionai/corso/src/internal/connector/graph"
 	gapi "github.com/alcionai/corso/src/internal/connector/graph/api"
 	"github.com/alcionai/corso/src/internal/connector/onedrive/api"
@@ -126,7 +127,7 @@ func drives(
 
 		drives = append(drives, tmp...)
 
-		nextLink := gapi.NextLink(page)
+		nextLink := ptr.Val(page.GetOdataNextLink())
 		if len(nextLink) == 0 {
 			break
 		}